He added that without America’s backing, South Korea – which he said had a poor relationship with neighbouring Japan – would be fairly isolated on the global stage.

Yet Mr Yoon does not necessarily have the support or domestic approval ratings to publicly keep Mr Trump happy.

Instead, the country could see nuclear armament as its only guarantee of safety, Prof Kelly suggested.

“In short, if Trump will not fight for South Korea, and if he demands a huge protection fee too, then the argument for South Korea to go its own way grows dramatically,” he said.

“Indigenous nuclear weapons are the obvious replacement for a decaying US nuclear security commitment.”